1. Field of the Invention
The present invention relates to a photoelectric detector and, more particularly, to a photoelectric detector using a pyroelectric polymer film as a photosensor or light-sensing element.
2. Brief Description of the Prior Art
It is known that a piezoelectric polymer material such as polyvinylidene vinylidene or the like has also a pyroelectric property. This pyroelectric property can be utilized for an opto electro transducer of which a photoelectric detector is composed. Such an opto electro transducer can be used as a sensing element for a detector such as a fire alarm or an intrusion alarm, an optical calorimeter for measuring the output of a laser beam or otherwise. In particular, the pyroelectric polymer film can provide an element of a large area having a uniform distribution in pyroelectricity so that it is useful for an optical calorimeter having a high output with less dependence upon beam diameters. An opto electro transducer resulting from such a polymer material having a polarity, such as polyvinylidene fluoride or the like can be obtained by polarizing the material at a voltage and a direct current. The opto electro transducer is mounted on a frame to make a photoelectric detector. The photoelectric detector is constructed such that light transmitted into the opto electro transducer is converted to electric outputs thereby with the strength of the light, thereby measuring or detecting the light.
As the opto electro transducer also has a piezoelectric property, there is a disadvantage that a pressure being applied from the ambient environment or a disturbance from the outside, such as a sound or wind may cause vibration of the opto electro transducer and consequently the output voltage is caused to occur in association with or in accordance with the vibration of the transducer. Accordingly, such a disturbance may result in a misoperation or an error in measurement. In order to prevent the disturbance from being caused, it is proposed to place an opto electro transducer in a space which is controlled so as not to undergo an influence from a disturbance. This requires a provision of two disturbance-preventive chambers with a transducer mounted therebetween. This also causes a temperature differential between the two chambers with the energy of incoming light absorbed by the transducer giving rise to a cause of noises. In this system, the disturbance-preventive chambers are closed air-tightly, so that a pressure differential is caused to occur between the two chambers. This pressure differential also results in noises.